Update Oceanverse.md

Oceanverse.md

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-13.Consider the function $$\phi : \mathbb{R}^2\rightarrow \mathbb{R}^2$$ defined by $$\phi (x,y)=(2x+3y,3x+4y)$$. What has this to do with the simultaneous equations?
+13.Consider the function $$\phi : \mathbb{R}^2\rightarrow \mathbb{R}^2$$ defined by $$\phi (x,y)=(2x+3y,3x+4y)$$. Find x and y such that $$\phi (x,y)=(5,6)$$. Obseve that (5,6) as well as (x,y) lies in $$\mathbb{R}^2$$.
 
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    <summary>Sol.</summary>